Numerous types of floor and wall covering materials have heretofore been developed. In general, all such products seek to achieve two important but not necessarily consistent goals: aesthetic appearance and wear resistance. Of particular importance in many of these products is the achievement of a floor covering product in which the aesthetic appearance itself is resistant to wear. Such a feature helps to ensure that the basic "look" of the product does not change as the product is used.
With respect to aesthetics, it has particularly been a goal of the prior art to create decorative flooring products having a three dimensional appearance or the appearance of visual depth. Flooring products with these effects are frequently referred to as "inlaid," and such prior art inlaids have heretofore been associated with one of two basic classes of products.
The first class of inlaid product is formed by depositing a granular resin composition through openings in stencil plates onto a backing layer, the openings in the stencil plates defining the outline of the individual inlays. An example of this method is disclosed in U.S. Pat. No. 3,325,574. The backing layer is fed from a roll over an inlaying table. After each stenciling operation, the backing is fed or moved at a distance equal to the effective width of the stencils and additional granulated compositions of other colors or shades are applied at such intervals until the entire composite inlaid pattern is formed on the backing. Thereafter, the inlays are consolidated under heat and pressure to form a smooth surfaced sheet. The product is sometimes embossed in a subsequent operation, after which the final product is cooled and formed into a roll. Because this first class of product is made using multiple steps, it is unfavorably tedious and cumbersome. Additionally, the equipment used in this process is complex and costly.
In the second basic class of products, as is shown in FIG. 1, decorative effects are produced by incorporating decorative particles, chips or flakes 10 into one or more layers 15 of the surface covering. These decorative particles are present substantially uniformly in the wear or other layer and are individually visible or discernable by persons viewing the flooring product.
The decorative particles in this second class of inlaid products are typically incorporated into the surface covering by one of two methods. In the first method, the decorative particles are distributed in a substantially uniform fashion over the entirety of a fluid plastisol layer. By way of example, U.S. Pat. No. 4,212,619 discloses the deposition of a layer of decorative particles onto a moving and vibrating web coated with a tacky, ungelled vinyl plastisol. This is followed by compressing the particles and the ungelled plastisol into a single layer by the use of pressure and thereafter gelling the plastisol at an elevated temperature. The gelled plastisol having the particles embedded therein is then fused to permanently fix the particles. Such a method is also considered cumbersome, as well as inefficient, generally involving application of the particles by sprinkling them onto a resinous surface to which they adhere and/or in which they can be embedded. Not only do agglomerates of the particles tend to form and clog the equipment, but the sprinkling of the particles leads to uneven distribution in the receiving surface because the particles tend to stick together.
In the second method, the decorative particles are instead dispersed, suspended or otherwise incorporated in the plastisol prior to application of the plastisol onto a backing sheet. As disclosed in U.S. Pat. No. 4,126,727, the decorative particles may be thoroughly blended into a polymer wear layer composition, which is then formed into a preformed, self-supporting sheet material by a calendering process. The preformed sheet is then laminated to a first resinous polymer layer. Alternatively, the decorative particles may be dispersed throughout a fluid material used to form the inlaid layer of the sheeting. For example, as disclosed in U.S. Pat. No. 5,178,912, a fluid vinyl plastisol is utilized as a carrier medium for the decorative particles. The plastisol and particles incorporated therein are then applied by a reverse roll coater to the receiving surface of the sheeting.
U.S. Pat. No. 5,338,504 similarly discloses a fluid material having decorative particles dispersed therein. A transparent or translucent layer containing plate-like particles is cast, after which a plurality of jet streams is directed onto the layer in order to reorient the particles at various angles with respect to the surface. Because the plate-like particles are substantially reflective to light, light is reflected at various angles as it passes within the layer, which is said to create an enhanced three dimensional effect.
The second basic technique for creating an "inlaid" product involves fewer steps and is, as a result, less time consuming and less costly, than the first basic technique. However, even this improved technique is inevitably limited with respect to the potential for design variations. The decorative particles may be sprinkled or mixed, compressed or reoriented, colored or pearlescent, reflective or nonreflective, discernable or not discernable. However, the particles will always remain distinct and any resulting design will necessarily be dependent at least to some extent on the geometry of the particles. The decorative possibilities of such inlaid products are thus unavoidably limited by the orientation, appearance and geometry of the individual particles. As a result, this technique provides no possibility to form continuous and varied gradations of color and shape as part of the wear layer. Furthermore, this technique provides no options to blending or harmonizing varied or dissimilar colors.
It is therefore an object of this invention to provide a method of manufacturing a decorative surface covering wherein the design or decorative effect lies within the wear surface itself, thereby eliminating the need for, but retaining the option of, a separate printed design layer.
It is an additional object of this invention to provide a method of manufacturing an inlaid-type decorative surface covering which does not require the positioning of discrete particles within a plastisol composition to obtain design effects.
It is a further object of this invention to provide a decorative surface covering which is capable of producing a three dimensional appearance and which is likened to natural formations such as marble or granite.
It is an even further object of this invention to provide a method of manufacturing decorative surface coverings which comprises relatively few steps.